Re: How much we can trust packet timestamping

Alan Cox (alan@lxorguk.ukuu.org.uk)
30 Dec 2002 13:09:03 +0000

On Mon, 2002-12-30 at 11:28, uaca@alumni.uv.es wrote:
> Hi all
>
> IMHO The problem is quite complicated because
>
> + common hardware is not designed for real time:
>
> - sends multiple PDUs within one interrupt, and can be delayed
> - Host adapter bus & infraestructure is not designed to garantee latency
> etc...

The packet can be timestamped by the hardware receiving as well as by
the kernel netif_rx code. This is actually intentional and there is
hardware that supports doing IRQ raise time sampling which the driver
can then use to get very accurate data.

Alan

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